5.1 Exported definitions

5.1.1 Functions

Function: compressBUFFER INDEX LIMIT

Compresses the contents of BUFFER, a vector of (UNSIGNED-BYTE 8), from
position INDEX to position LIMIT. Returns two values, a vector of
type (UNSIGNED-BYTE 8) holding the compressed data and an integer indicating
the number of compressed octets in the vector.

We use eight bits for the length even though 7 would have sufficed
because of efficiency reasons:
(1) Extracting a byte is faster than a bit field
(2) It properly aligns copy offset so we do not need a <<8